Ducts provide transport passageways for a wide variety of applications. For example, ducts provide passageways for transporting gases for heating and ventilation in vehicles and buildings. Likewise, water distribution systems often use ducts for fluid transport. Ducts for the foregoing and other applications can be formed of metal, plastics, ceramics, composites, and other materials.
In HVAC (Heat Ventilation and Air Conditioning) systems, air passes through enclosed channels referred to as air ducts that communicate supply air from a central air handler via a centrifugal fan or blower to the various rooms of the building. Other ducts communicate return air from the rooms back to the central air handler for filtering, cooling, heating, and so forth. The supply air and even more so the return air ultimately contains dust, debris, and microbial contaminates. Gradually over time, some of these particulates accumulate on the interior walls of the air ducts. Excessive accumulation of these particulates degrades the performance of the air duct system by impeding necessary air flow. Similarly, significant portions of these contaminants can be redistributed to the air supply. Regular cleaning and maintenance activities eliminate a portion of the contaminants. Routinely changing the filters in an HVAC system will help remove air borne particles, but only to the degree that the filter is rated and only until the filter becomes loaded with debris.
The return duct is the dirtiest and most germ filled duct in air duct systems. All dirt gets stuck in the bottom, sides, and top of the duct. When some of the particles finally reach the filter, then they get trapped in the filter. The benefit of cleaning out the duct system is that by washing and decontaminating the ducts, germs, dustmites and other harmful bacteria are flushed out. In addition, when there is a good filter the heat and air conditioning system can perform better, reducing energy costs. There are some filters claiming that they can clean the air up to 99.9%, provided that the user maintains it, however, such claims belie the fact that the ducts remain full of contaminants without regular thorough cleanings.